Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.63	12.863%	$167.7483	$167.75	$167.75	$167.70
Purchase #2	$241.41	6.633%	$257.4227	$257.42	$257.40	$257.40
Purchase #3	$13.98	8.458%	$15.1624	$15.16	$15.15	$15.20
Purchase #4	$121.30	8.667%	$131.8131	$131.81	$131.80	$131.80
Purchase #5	$206.77	9.258%	$225.9128	$225.91	$225.90	$225.90
Purchase #6	$200.79	10.466%	$221.8047	$221.80	$221.80	$221.80
Purchase #7	$72.94	7.645%	$78.5163	$78.52	$78.50	$78.50
7 purchase totals =	$1,005.82		$1,098.3803	$1,098.37	$1,098.30	$1,098.30